Forum,

My 2008 550i is overheating. The following parts have been changed and has not resolved the problem:

Thermostat - Not the issue
Auxiliary Electric Water Pump - Not the issue

Coolant Level is within specifications.

Reasons the car is or is not overheating:

1. If the AC is turned off and the heater is on the car does not over heat.
2. If the AC is turned on the car overheats at idle or at a red light. The air conditioner stops blowing cold and the Temputer Warning Indicator comes on. If I turn off the AC and turn on the Heater the car does not overheat. I also opened the hood and found the fan was not spinning while the AC was on and the engine was starting to overheat.

Talked to a couple of "experts" and they are telling me the whole fan needs to be replaced or a relay.

Has anyone else had this issue? I don't want to just keep on replacing parts and not diagnoise the issue.

Thanks.

 

the fan should cycle on, especially after a warm start, and spin pretty well. if it is not spinning check it by applying 12V to the correct pins on the fan's connector; if it starts spinning, you need a new relay. if it doesn't spin, something's wrong with the fan, check for obstructions or gunk built up, and if there's none, time for a new fan.

might want to check the fan fuse(s) as well if they are fused like they should be.

HTH

 

check to see if your electric radiator fan kicks on.

 

The fan isn't kicking on when the engine needs it the most. The fan cut off relay is a built in part of the fan assembly. The dealer said I would have to replace the whole fan assembly to replace the fan cut off relay. I have ordered the assembly but it hasn't come in yet. It is a "special order" part. Im hopping this $700 plus part is the problem.

 

I am having the same overheating problem. Where you able to track it down?

 

Did you check the water pump? It has a plastic impeller.

 

I would go with what "545iFelix" is saying he hit the answer right on the spot but my opinion I think it's the Relay that's out .

 

I am having the same problem. I put in a new thermostat and when that didn't fix the problem i was told the new thermostat was bad, so I Put another thermostat in and it didn't fix the issue? I cant find any information on the fan relay location?

 

Does your fan work when tested with the 12V as mentioned above? If so then maybe you have a bad coolant temp sensor located on the lower radiator hose, as this sensor sends a signal to turn the fan on when coolant temp is too hot. Check in the trunk area where the battery is located; the relay could possibly be there however I'm not exactly sure where it is.

 

didn't see it mentioned - does it overheat when you're driving over 30mph? or only while stopped? if it's only a problem when you're not moving, then the main fan is definitely suspect. at speeds >30mph, the fan isn't really needed.